Ethylsilicate polymers and ethylsilicate binders are used in a variety of applications in various industries. Common uses include coatings, sealants, consolidents, and other uses in the investment casting industry. Ethylsilicate binders are typically mixed into other products for use in commercial and industrial applications. For example, in the coatings industry, the ethylsilicate binder may be mixed with other materials to create an inorganic zinc-rich primer for coating metals against corrosion or before application of paint. In the casting industry, ethylsilicate binders are mixed in with other materials to form the casting material into a hardened ceramic material.
Traditional ethylsilicate binders include various VOCs that are released during the application and use of the product and while the product cures. Many of the VOCs included in traditional ethylsilicate binders are regulated by various governmental agencies, such as the Environmental Protection Agency in the United States of America. In most ethylsilicate polymers the majority of regulated VOCs come from the ethanol or other alcohols, and the solvents that are typically used to keep the silica from gelling during manufacture, transportation, storage and use. For example, in the coatings industry, ethylsilicate binders when used in inorganic zinc-rich primers generally include a ketone or an ether as a solvent, such as at least one of methyl n-amyl ketone (MAK), dipropylene glycol monomethyl ether (also known as glycol ether DPM) and ethanol, which are subject to various VOC regulations. There are many other regulated solvents. The ethanol, MAK, and DPM are also common in ethylsilicate polymers in the investment casting industry. These ethylsilicate binders, which include the above identified chemicals and solvents, which are regulated as VOCs, are well known and produce products with long-term stability, easy manufacturing processes, high product performance, consistent product quality, and easy transportation and storage. As these ethylsilicate polymer binders in common use generally use at least one of the above regulated solvents, and include ethanol, when they are used in commercial or industrial applications, the user, whether as a value added manufacturer or an end user, typically must monitor the amount of VOCs included in the product and the release of the regulated VOCs and comply with various restrictions on their application and use. If a user exceeds specified levels, the user must take steps to mitigate which may be costly and require substantial time and effort to ensure compliance with various regulations. As such, any reduction in regulated VOCs, in the end product, even if the ethylsilicate polymer is only a part of the end product, may save the user substantial costs, time and effort.
As many regulations regarding VOCs regulate such VOCs by measuring by what is in the product at the time of shipment, the use of ethylsilicate binders including regulated VOCs, in addition to any ethanol created or added during the manufacturing process, adds complexity and expense for the user, if the regulated VOCs exceed the regulated thresholds. Therefore, many users of ethylsilicate polymers desired reduced regulated VOC products. However, as the industries where ethylsilicate polymers are used are typically highly technical with strict performance requirements, any reduction in performance characteristics with a product having lower regulated VOC levels would be unacceptable.
Some manufacturers have attempted to use water-based solvents that do not include regulated VOCs in place of solvents containing regulated VOCs in ethylsilicate polymers or binders in order to reduce the amount of regulated VOCs. First, changing the solvents alone does not eliminate regulated VOCs, as the product still includes ethanol and other alcohols. However, these known substitute solvents, particularly water based solvents when used in ethylsilicate polymer binders, have substantial performance, longevity and other issues and have not been adapted by industry. More specifically, most ethylsilicate polymer binders have a natural tendency to gel or precipitate out of the solvent, making them generally unstable, particularly during storage, transportation, and subsequent use to create other products. In making ethylsilicate polymers, the manufacturer is constantly making sure the product does not gel or precipitate out of solution, as any minor change in formulation generally causes these negative results. As such, no solvent substitution has had commercial acceptance because the resulting ethylsilicate polymer had substantial reduced performance characteristics. In particular, water-based solvents create ethylsilicate binders that are not stable, both during the manufacturing process as well as during transportation and storage. In addition, as many users combine the ethylsilicate polymer with other materials to form a final product. Ethylsilicate polymers in water-based solvents are typically unstable, as they have been found to react with many other materials causing the silica to gel or precipitate out. Specific problems with ethylsilicate polymers using water-based solvents include a tendency to gel, which makes them unusable for most desired applications. Temperature changes during transportation and storage of the product are also problematic in ethylsilicate binders formed with water-based solvents. Even if the solvent is not water-based, manufacturers have not to date found a solvent with low to no regulated VOCs that may be substituted for the typical MAK or glycol ether DPM solvents that retain substantially similar performance characteristics. Currently, all solvent substitutions for these traditional solvents, whether water-based or not, have not been able to provide the long term stability, consistent quality and consistent performance considerations and furthermore are especially not stable during use, temperature changes, transportation, and subsequent use into a final product. More specifically, it has been found that solvent substitutions, whether water-based or not, tend to cause the ethylsilicate materials to gel which makes them unusable for the desired applications. With some solvents, the ethylsilicate material may even suddenly gel during the manufacturing process creating substantial problems, and most solvent substitutions at a minimum cause the ethylsilicate polymer to partially gel, which is also unacceptable and creates numerous problems, including precipitation of the silica out of the material, all of which makes the product unfit for its intended purpose. These problems may even ruin the equipment used with ethylsilicate polymer under certain conditions.
In view of the above issues, there is a need for an ethylsilicate polymer binder with low or reduced regulated VOCs which is highly stable during the manufacturing process, transportation, storage, and final preparation into an end use product, including contributing to stable storage and use of such end use product, with consistent, repeatable and high performance characteristics during use or application by the ultimate user. Having non-regulated chemicals as solvents or an overall product with reduced regulated VOC levels may allow the end user to avoid otherwise necessary and expensive regulatory compliance steps required by existing ethylsilicate polymer binders. Even if the ethylsilicate binder still includes some regulated VOCs such as ethanol, the reduction in VOCs may allow for reduced regulatory compliance as well as reduction in the time-consuming and expensive steps in complying with certain regulatory requirements as compared with products having regulated VOCs. To date, no ethylsilicate polymer binder having low or reduced amounts of regulated VOCs is available with acceptable or improved performance characteristics.